Food processing and production

Question 1

What is primary processing?

Answer 1

• Prepares raw food to be eaten, cooked immediately or used as an ingredient

Question 2

How is wheat processed to produce flour?

Answer 2

• A wheat grain is made of bran (mostly fibre), endosperm (mostly starch) and germ (vitamins, protein and fat)
• Wheat grains are harvested and then cleaned to removes any stones or dust
• Water softens the outer layer (bran) of the grain
• It’s blended with other types of wheat in a process called gristing
• The grist is passed through fluted break rolls rotating at different speeds so the wheat is sheared open
• The fragments of the wheat are separated by sieves
• The endosperm go through reduction rolls for final milling
• Coarser pieces of bran are passed through the rolls again
• In the end, wheat is separated into flour, germ and bran

Question 3

What are 3 different types of flour, their components and extraction rates?

Answer 3

• Wholemeal flour contains all of the parts of wheat grains, and so has an extraction rate of 100%
• Brown flour does not contain the bran, so it had an extraction rate of 85-90%
• White flour has an extraction rate of 70-75% as it doesn’t contain the germ or the bran

Question 4

What is milk like, and what is done to it as a result?

Answer 4

• Milk is an emulsion of oil in water, so the fat rises to the top and creates a cream line
• Homogenisation is the process of forcing milk at high pressure through small holes, which breaks up fat globules
• This spreads them out evenly in the milk

Question 5

Why is milk heat-treated, and list 3 ways this is done.

Answer 5

• To destroy pathogenic bacteria
• Pasteurised: heated to at least 72°C for 15 seconds, then cooled below 6°C
• Sterilised: heated at 110°C for 10-30 minutes, then cooled
• Ultra heat treatment (UHT): heated to 135°C for 1 second and put into sterile, sealed containers

Question 6

List 2 issues with heat-treated milk.

Answer 6

• All of the bacteria in sterilised milk is killed, so it tastes different and many group B and C vitamins are lost
• UHT milk has slightly less nutritional value and a different taste to pasteurised milk

Question 7

How are fruits and vegetables processed to become a food product?

Answer 7

• Fruits and vegetables are washed with water to remove dirt, insects and chemical sprays
• They’re sorted into different sizes and shapes
• Pits are removed
• They’re squeezed for juice/ dried/ crushed or pressed to extract oils

Question 8

How is meat processed?

Answer 8

• Some (like beef) are hung and dried to make them more tender and improve their flavour
• The feathers and internal organs of poultry are removed
• The wings and legs of poultry are tied so it cooks evenly
• Meat is chopped, sliced or cut

Question 9

How is cream made?

Answer 9

• The fat in milk rises to the top as it is less dense, and can be ‘skimmed off’ (to aid the separation, milk is rotated at a fast speed)
• The cream is then pasteurised to kill pathogenic bacteria and enzymes that affect its taste and would shorten its shelf life
• Different types of cream have different amounts of milk fat (single cream has 18%, and double cream has 48%)

Question 10

How is butter made?

Answer 10

• Cream is churned to remove more liquid
• This agitates the cream until the fat droplets stick together
• The cream gets thicker until it forms a solid mass of butter
• Butter has a fat content of between 80 and 90%

Question 11

How is cheese made?

Answer 11

• The milk is pasteurised to kill pathogenic bacteria
• Bacteria is added to turn lactose into lactic acid to help coagulate the protein in milk, preserve the cheese and to develop a sour flavour
• Rennet is added and the mixture sets into solid cheese curds
• The whey (remaining liquid) is removed
• In soft cheese it is allowed to drain away naturally, but in hard cheeses the curds are heated and piled on top of each other to remove more whey
• The cheese is milled, salt added for certain types, and pressed into moulds
• It is left to mature
• Bacteria or mould may be added to change the flavour

Question 12

How is yoghurt made?

Answer 12

• The milk is pasteurised and homogenised
• Bacteria are added that that change lactose to lactic acid, which causes it to coagulate (thicken) and gives it a sour taste
• The yoghurt is left until it reaches the correct level of acidity
• Fruit and flavourings are added

Question 13

How is pasta made from flour?

Answer 13

• It is mixed with eggs or water
• The dough is shaped by forcing it thorugh a metal die, and it is then folded or twisted
• Colourings may be added
• Pasta is then sold either fresh or dried

Question 14

How is bread made from flour?

Answer 14

• Flour is mixed with water and yeast to make a dough
• The dough is kneaded to develop the gluten
• The dough is proved to let the yeast ferment
• The dough is baked in the oven

Question 15

How are foods canned?

Answer 15

It’s a from of sterilisation.
- Food is either packed into a can and then sterilised
- Or it can be sterilised and placed in aseptic cans
- They’re then sealed to prevent leakage and contamination

Question 16

What are 2 disadvantages of caning foods?

Answer 16

• Their texture might change
• Canned foods lose B group vitamins and vitamin C

Question 17

List 5 low temperature methods of preserving food. Why do they work?

Answer 17

They slow down the speed that bacteria reproduce at, and freezing food makes bacteria dormant.
- Chilling
- Freezing
- Cook-freeze
- Blast chilling
- Accelerated freeze- drying (AFD)

Question 18

How are foods chilled?

Answer 18

• They’re cooled to between 0 and 5°C

Question 19

How are foods frozen?

Answer 19

• They’re cooled to -18°C

Question 20

What does it mean to cook-freeze a food?

Answer 20

• The food is cooked, then rapidly frozen

Question 21

What is blast chilling?

Answer 21

• Blast-chillers rapidly cool cooked food to below 5°C within 90 minutes

Question 22

What is accelerated freeze-drying (AFD)?

Answer 22

• Food is rapidly frozen and dehydrated to remove moisture
• Adding water to the food restores the food to its original texture and taste

Question 23

Describe drying foods.

Answer 23

It works as microorganisms need moisture, so without it they cannot grow.
- Hot or warm temperatures are used to remove the moisture
- Dried foods need to be stored in a cool, dry place
- Their colour, taste, texture and nutritional value can be affected

Question 24

What impact does smoking foods have?

Answer 24

• The food is dipped in salt or an acid solution first
• Chemicals in the wood being burnt give it flavour and help preserve it

Question 25

How do acids, salt and sugar preserve food?

Answer 25

• They either kill bacteria or stop them from reproducing
• Bacteria cannot survive beneath a pH of 4.5 (vinegar’s pH is 3.5)
• Salt reduces moisture by osmosis
• In high enough concentrations (over 60% of the product) sugar makes water unavailable, so bacteria cannot grow

Question 26

What is monitored/ controlled atmosphere packaging (MAP/ CAP)?

Answer 26

• It slows down the growth of microorganisms as they use oxygen for growth, which increases the shelf life
• Fresh foods are packaged
• The air around it is replaced through ‘gas flushing’ (different proportions of oxygen, nitrogen and carbon dioxide according to the food)
• Sealed with a plastic bag or lid to make the container airtight
• As a result once the container is opened, the food has a regular shelf life
• It is used for chilled meat, fruits and vegetables

Question 27

What is vacuum packing?

Answer 27

• Air is removed from the package and it is sealed
• The food is kept in anaerobic conditions, which prevents bacteria from growing
• Once opened it has a regular shelf life
• The food maintains its colour and texture